| Message ID | 20230221112157.418648-1-kkostiuk@redhat.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | QGA installer fixes | expand |
On 21/2/23 12:21, Konstantin Kostiuk wrote: > resolves: https://bugzilla.redhat.com/show_bug.cgi?id=2167423 > fixes: CVE-2023-0664 > > CVE Technical details: The cached installer for QEMU Guest Agent in c:\windows\installer > (https://github.com/qemu/qemu/blob/master/qga/installer/qemu-ga.wxs), > can be leveraged to begin a repair of the installation without validation > that the repair is being performed by an administrative user. The MSI repair > custom action "RegisterCom" and "UnregisterCom" is not set for impersonation > which allows for the actions to occur as the SYSTEM account > (LINE 137 AND 145 of qemu-ga.wxs). The custom action also leverages cmd.exe > to run qemu-ga.exe in line 134 and 142 which causes an interactive command > shell to spawn even though the MSI is set to be non-interactive on line 53. > > v1: https://lists.nongnu.org/archive/html/qemu-devel/2023-02/msg05661.html Per https://lore.kernel.org/qemu-devel/CAA8xKjUQFBVgDVJ059FvGoSjkv+kZ5jB1gfMNz+ao-twH7FDRg@mail.gmail.com/: Reported-by: Brian Wiltse <brian.wiltse@live.com> > v1 -> v2: > Add explanation into commit messages Thanks, much appreciated! > Konstantin Kostiuk (2): > qga/win32: Remove change action from MSI installer > qga/win32: Use rundll for VSS installation > > qga/installer/qemu-ga.wxs | 11 ++++++----- > qga/vss-win32/install.cpp | 9 +++++++++ > qga/vss-win32/qga-vss.def | 2 ++ > 3 files changed, 17 insertions(+), 5 deletions(-) > > -- > 2.25.1 >
ping On Tue, Feb 21, 2023 at 1:41 PM Philippe Mathieu-Daudé <philmd@linaro.org> wrote: > On 21/2/23 12:21, Konstantin Kostiuk wrote: > > resolves: https://bugzilla.redhat.com/show_bug.cgi?id=2167423 > > fixes: CVE-2023-0664 > > > > CVE Technical details: The cached installer for QEMU Guest Agent in > c:\windows\installer > > (https://github.com/qemu/qemu/blob/master/qga/installer/qemu-ga.wxs), > > can be leveraged to begin a repair of the installation without validation > > that the repair is being performed by an administrative user. The MSI > repair > > custom action "RegisterCom" and "UnregisterCom" is not set for > impersonation > > which allows for the actions to occur as the SYSTEM account > > (LINE 137 AND 145 of qemu-ga.wxs). The custom action also leverages > cmd.exe > > to run qemu-ga.exe in line 134 and 142 which causes an interactive > command > > shell to spawn even though the MSI is set to be non-interactive on line > 53. > > > > v1: > https://lists.nongnu.org/archive/html/qemu-devel/2023-02/msg05661.html > > Per > > https://lore.kernel.org/qemu-devel/CAA8xKjUQFBVgDVJ059FvGoSjkv+kZ5jB1gfMNz+ao-twH7FDRg@mail.gmail.com/ > : > > Reported-by: Brian Wiltse <brian.wiltse@live.com> > > > v1 -> v2: > > Add explanation into commit messages > > Thanks, much appreciated! > > > Konstantin Kostiuk (2): > > qga/win32: Remove change action from MSI installer > > qga/win32: Use rundll for VSS installation > > > > qga/installer/qemu-ga.wxs | 11 ++++++----- > > qga/vss-win32/install.cpp | 9 +++++++++ > > qga/vss-win32/qga-vss.def | 2 ++ > > 3 files changed, 17 insertions(+), 5 deletions(-) > > > > -- > > 2.25.1 > > > >
Microsoft has a list of best practices for MSI creation which covers custom actions https://learn.microsoft.com/en-us/windows/win32/msi/windows-installer-best-practices#if-you-use-custom-actions-follow-good-custom-action-practices, The change to the custom action from an interactive command shell to a silent invocation of rundll32.exe keeps the interactive shell from being easily caught and abused, but this does not fully solve the repair from being triggered from a non admin user. There is still the potential for abuse indirectly via attacks like the Mitre documented Hijack Execution Flow technique - Path Interception by PATH Environment Variable (https://attack.mitre.org/techniques/T1574/007/), or even the abuse of potential arbitrary folder creates, file writes and deletes in user-controlled areas such as C:\ProgramData. The Change button was removed from "Programs and Features", but the cached installer in c:\windows\installer can be leveraged directly to start a privileged repair with msiexec.exe as a non-administrative user. Ideally, the MSI would be compiled with the Privileged property https://learn.microsoft.com/en-us/windows/win32/msi/privileged or AdminUser property https://learn.microsoft.com/en-us/windows/win32/msi/adminuser or InstallPrivileges="Elevated" https://wixtoolset.org/docs/v3/xsd/wix/package/ or similar privilege check that which would help ensure the user has proper privileges to perform the repair or change action. However, since the QEMU build process leverages WiXL from msitools, many of the WiX property types are not currently supported to leverage as solutions ( i.e. (wixl:1077): GLib-GObject-WARNING **: 17:49:05.477: g_object_set_is_valid_property: object class 'WixlWixPackage' has no property named 'InstallPrivileges' ). This similar to wixl issue 40 https://gitlab.gnome.org/GNOME/msitools/-/issues/40. I do see that Wixl appears to support the custom action JScriptCall. This might provide for a facility for a script could be run to check if the user has the proper privileges before privileged actions are taken in the repair process, but this is not an ideal solution. Thanks, Brian
Hi Brian, Konstantin, On 28/2/23 23:48, Brian Wiltse wrote: > Microsoft has a list of best practices for MSI creation which covers > custom actions > https://learn.microsoft.com/en-us/windows/win32/msi/windows-installer-best-practices#if-you-use-custom-actions-follow-good-custom-action-practices <https://learn.microsoft.com/en-us/windows/win32/msi/windows-installer-best-practices#if-you-use-custom-actions-follow-good-custom-action-practices>, The change to the custom action from an interactive command shell to a silent invocation of rundll32.exe keeps the interactive shell from being easily caught and abused, but this does not fully solve the repair from being triggered from a non admin user. There is still the potential for abuse indirectly via attacks like the Mitre documented Hijack Execution Flow technique - Path Interception by PATH Environment Variable (https://attack.mitre.org/techniques/T1574/007/ <https://attack.mitre.org/techniques/T1574/007/>), or even the abuse of potential arbitrary folder creates, file writes and deletes in user-controlled areas such as C:\ProgramData. > > The Change button was removed from "Programs and Features", but the > cached installer in c:\windows\installer can be leveraged directly to > start a privileged repair with msiexec.exe as a non-administrative user. > Ideally, the MSI would be compiled with the Privileged property > https://learn.microsoft.com/en-us/windows/win32/msi/privileged > <https://learn.microsoft.com/en-us/windows/win32/msi/privileged> or > AdminUser property > https://learn.microsoft.com/en-us/windows/win32/msi/adminuser > <https://learn.microsoft.com/en-us/windows/win32/msi/adminuser> or > InstallPrivileges="Elevated" > https://wixtoolset.org/docs/v3/xsd/wix/package/ > <https://wixtoolset.org/docs/v3/xsd/wix/package/> or similar privilege > check that which would help ensure the user has proper privileges to > perform the repair or change action. However, since the QEMU build > process leverages WiXL from msitools, many of the WiX property types are > not currently supported to leverage as solutions ( i.e. (wixl:1077): > GLib-GObject-WARNING **: 17:49:05.477: g_object_set_is_valid_property: > object class 'WixlWixPackage' has no property named 'InstallPrivileges' > ). This similar to wixl issue 40 > https://gitlab.gnome.org/GNOME/msitools/-/issues/40 > <https://gitlab.gnome.org/GNOME/msitools/-/issues/40>. > > I do see that Wixl appears to support the custom action JScriptCall. > This might provide for a facility for a script could be run to check if > the user has the proper privileges before privileged actions are taken > in the repair process, but this is not an ideal solution. Does that mean this patchset is, although "not ideal", sufficient to fix CVE-2023-0664? Or does this need more work? (IOW, do we feel happy enough and want to merge this and forget about it?) Konstantin, you use "Fixes: CVE-2023-0664" in two different patches. I'm worried a downstream distrib only pick one and feel safe. Maybe use something like "Fixes: CVE-2023-0664 (part 1 of 2)".
Hello, I think this patch is sufficient to remediate the priv ledge escalation via the repair and catching the VSS com registration boxes that were being invoked frivolously. Long term the repair function not validating if the user has admin should be addressed as well since their is still a potential for abuse. I dont see any other easy privledge elevation vulns at the moment other then an potential arbitrary file create where the creation of C:\programdata\qemu\qemu-ga.pid could be potentially be redirected via symbolic links to another file, but I have not been able to find time to fully prove that out. If we could get wixl support for the user privilege checks this would close abuse via the installer repair. Thanks, Brian